Sierra Nevada Brewing Company released a timelapse video of the open tank fermentation process used to make their famous Bigfoot Barleywine. For those of you who have never seen a high gravity beer fermentation this may seem pretty chaotic. The stainless steel vessels are cleaned, sanitized, then filled with cooled wort on which the yeast is pitched. The bubbly foam you see moving around on top/spilling over the side is referred to as the krausen. This is yeast and wort proteins, along with unfermentables and hop resins. It usually sticks to the side of the fermenter, and in this case spills over the sides of the vessel. Pretty amazing to see this process in timelapse! Great video Sierra Nevada!
Why Use A Stir Plate?
Stir plates are a great way to increase the potential of your yeast. By constantly stirring your yeast starter you can increase the amount of Oxygen in your solution, knock CO2 out of suspension, and keep the yeast in constant contact with the nutrients it needs to reproduce. With the power of these forces combined your yeast becomes Captain Planet! Actually what it really does is create much more yeast cells (with healthy cells walls) than your typical smack pack or dry yeast pack. Stir plates generally cost anywhere from $60 – $100 (and sometimes more). I’ve found a great thread on Homebrewtalk.com that walks you through building your own on the cheap. There is also another good one at Brewiki.org.